In a typical communication system, multiple base stations may be utilized to serve many remote units. The coverage area of each base station usually overlaps the coverage area of other base stations in order to give complete coverage of a geographic area. In a typical scenario, communication to and from each base station will be allowed within a particular frequency band. The frequency bands of co-located base stations typically do not overlap. This is illustrated in FIG. 1.
As shown in FIG. 1, base stations 101, 102, and 103 each serve coverage areas 104, 105, and 106, respectively. As is evident, the coverage areas overlap somewhat (shaded area). In typical network planning, each base station 101, 102, 103 will be given a frequency band for all uplink communications from user equipment (UE). In FIG. 1, base station 101, 102, and 103 are given frequency bands 107, 108, and 109, respectively.
When frequency bands for co-located base stations are adjacent in frequency, spectrum at the band edges is reserved for use as a guard band to mitigate interference between adjacent spectrum band users that may also be co-located in the same geographic region. This is illustrated in FIG. 2 as guard bands 201. Furthermore, guard bands may be enlarged to compensate for worse case operating conditions, such as a UE simultaneously attempting to receive while in close proximity to other UE operating in an adjacent spectrum band attempting to transmit.
Typically, no transmissions are allowed to take place within a guard band. Because of this, the amount of spectrum being used is greatly reduced. It would be beneficial if somehow this spectrum were able to be utilized for communications. Therefore a need exists for a method and apparatus for allocating spectrum in wireless communication systems that allows for communications to take place within guard bands, yet does not cause interference within co-located base stations operating in adjacent spectrum.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Those skilled in the art will further recognize that references to specific implementation embodiments such as “circuitry” may equally be accomplished via replacement with software instruction executions either on general purpose computing apparatus (e.g., CPU) or specialized processing apparatus (e.g., DSP). It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.